A shield case has been used for protecting electromagnetic wave interference between electronic parts and electronic circuits mounted on a printed circuit board in a high frequency operating electronic circuit, for blocking the electromagnetic effect thereof to the outside and for preventing malfunction thereof (EMI protection function). A frame is used for supporting the printed circuit board in an electronic equipment.
A copper member is generally used for the shield case. However, there are cases of using a metal member (hereinafter referred to as “base material”) such as an albata material (Cu—Zn—Ni/C7521R, C7701R, etc.), stainless steel and other Kobar (Kovar/KOV-H; Fe—Ni—Co, etc.) from characteristic viewpoints of antimagnetic, anticorrosive, oxidation-resistant, heat expansion resistant and workability wherein Kobar is an alloy compounding nickel and cobalt to iron.
It is common that the base material as a case material, frame material, etc. has a predetermined width and elongated shape and is distributed under a condition that the base material is wound around a reel or the like in a roll (strip) type. The roll type wound base material is set to an automatic processing machine, is unreeled from the reel or the like, is punched out to a predetermined shape and is bending-processed to form the shield case or the frame.
As the electronic equipment is required to be compact and light weight and the electronic circuit is required to be high-density packaged, a method of plating (coating) the metal member as a material stage with the solder (hereinafter referred to as “solder coating method”) is applied to the shield case and frame. In the base material, a finish processing is slightly difficult for the albata material but easy for Kovar. It is known that a solderability is slightly good for the albata material but hard for Kovar.
A coating method is proposed in a method of adhering the solder on the printed circuit board wherein a predetermined volume of the solder is adhered on a land of the printed circuit board on which electronic micro-parts such as flip-chip parts, BGA or the like and micro-QFP are mounted. In this coating method, after a resist is adhered on an area except of the land on the printed circuit board, the printed circuit board is dipped in the molten solder and ultrasonic sound wave is applied to the molten solder in order to adhere the solder to the land (refer to Patent Document 1).
Another coating method is disclosed to previously achieve the plating of the land on the printed circuit board, a lead of the electronic part or the like. In this disclosed method, a work of the printed circuit board, electronic part, etc. is dipped in the jet molten solder to which the ultrasonic sound wave is applied. Then, the work is moved horizontally or back and forth with respect to an ultrasonic sound wave horn and the work is pulled up from a molten solder bath (refer to Patent Document 2).
A solder pre-coated film forming method and an apparatus thereof are disclosed wherein a tin or solder pre-coated film is formed on a micro-area electrode pad or a narrow pitch lead surface of the electronic circuit board or electronic part (refer to Patent Document 3). In this approach, when it is drawn up from the molten solder bath, the excess adhered solder film is blown down by blowing heated organic aliphatic acid solution. In addition, a coating material of plating the molten solder on a longitudinal soldering material is disclosed (refer to Patent Document 4).